Design and Development of Asymmetric Organocatalysts
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This thesis describes the design and synthesis of a new class of hydrogen bonding organocatalysts. After various synthetic strategies were investigated, a convenient two-step process, involving an amide coupling followed by borane reduction of the resulting N-acylsulfonamide, resulted in the formation of the targeted racemic 1,5-bis-sulfonamides. This synthesis also provided access to a second series of potential organocatalysts, the N-acylsulfonamides. The catalytic ability of both libraries of racemic compounds was tested in Friedel-Crafts type reactions of N-methylindole with ethyl glyoxylate and p-nitrostyrene. Following on from this work, a small number of N-acylsulfonamides were synthesised in enantiomerically enriched form, after resolution of the starting material trans-1,3-cyclohexanedicarboxylic acid using strychnine. Testing of the enantiopure N-acylsulfonamides showed that they were able to promote the Friedel-Crafts type reaction between N-methylindole and P-nitrostyrene, in good yields but poor enantioselectivities. A second group of catalysts were synthesised based on the TAD DOL class of compounds. Attempts to form his-sulfonamide TADDOL derivatives were unsuccessful, with only mono-sulfonamides being isolated, possibly due to a stabilising intramolecular hydrogen bond present in the mono-sulfonamides. A p-tolyl N-acylsulfonamide TADDOL derivative was also synthesised. The mono sulfonamide and N-acylsulfonamide TADDOL derivatives did not effectively catalyse the Friedel-Crafts type reaction between N-methylindole and P nitrostyrene. The TADDOL derivatives catalysed the model reaction between N methylindole and ethyl glyoxylate with low to moderate efficiency.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Physical Sciences
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In order to comply with copyright 2 diagrams have been removed from Chapter 1 page 3. This thesis has been scanned.
Hydrogen bonding organocatalysts
TAD DOL class of compounds